dt-bindings: RNG: Add Ingenic RNG bindings.

Add the RNG bindings for the JZ4780 SoC and
the X1000 SoC from Ingenic.

Signed-off-by: 周琰杰 (Zhou Yanjie) <zhouyanjie@wanyeetech.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>